1. Field of the Invention
The present invention relates to a device for collecting sheets such as those typically found in a copy machine.
2. Description of the Prior Art
U.S. Pat. No. 3,840,222 describes a device for collecting sheets with a collecting tray formed by a completely flat baseplate and a completely flat wall plate which adjoin one another at right angles and a conveyor roller which feeds sheets over the wall plate into the collecting tray. Two attractive advantages of this device in which the adjoining edge forms the lowest point of the baseplate are that when the device is disposed on the top of a sheet processing machine, such as a copying machine: (1) a relatively short feed path is required between the top of the machine and the conveyor roller at the collecting tray, and (2) the space between the collecting tray and the top of the machine is readily accessible for accommodating and reaching other facilities of the machine.
There are disadvantages, however, with this device. For example, when a sheet if fed into this collecting tray at relatively high speed, the sheet may stop on the baseplate in a position in which the sheet is at some distance from the wall plate and/or is skewed with respect to the wall plate. This incorrect positioning may occur particularly if lightweight and smooth sheets are deposited on a baseplate which is only slightly upwardly sloping or is downwardly sloping. Moreover, the last have landed correctly in the collecting tray can readily be displaced from their proper position by a subsequent sheet sliding over them as it is fed into the collecting tray.
The final position of a sheet is affected by the extent to which the sheet is slowed down in the collecting tray by sliding over the baseplate or sheets lying thereon. This slowing down is controlled by the angle of inclination of the baseplate, by the coefficient of friction between a sheet and the baseplate or between sheets relative to one another and by the weight of a sheet.
A disadvantage with a slightly upwardly sloping baseplate, such as described in U.S. Pat. No. 3,840,222, is that after a sheet has stopped in an incorrect position on the baseplate, the sheet cannot readily slide back into contact with the wall plate. This is particularly the case with heavy and stiff sheets which can readily jam on the baseplate. The object of the invention, therefore, is to provide a device without the above-mentioned disadvantages.
U.S. Pats. Nos. 3,907,128 and 4,380,332 both describe a tray particularly suitable for stacking rigid sheets such as glass sheets and die-cut blanks. Both of these trays are provided with a strip to which the leading edge of a sheet reaching the stacking position abuts for rebounding towards an abutment strip for the trailing edge. Thereafter, the sheet drops onto a platform or stack formed thereon such that the top level of the stack is held constant relative to the abutment strips. These devices present problems if used with paper. For example, rebounding does not occur with thin stacks or individual sheets of paper. Moreover, an intricate and complicated device is required to keep the top level of the stack constant relative to the abutment strips.
U.S. Pat. No. 3,160,413 and British Patent Application No. 2,017,622 both describe a tray provided with an arched platform. In U.S. Pat. No. 3,160,413 a pair of fingers arches the sheets as they are fed upon the platform, thereby holding the sheets in integral contact with each other. British Patent Application No. 2,017,622 accomplishes the same result using guide rails. Because both devices hold the sheets in integral contact with each other, neither is well suited for neatly stacking bundles of sheets which are stapled together.